1. Field of the Invention
The present invention relates to an iron core assembly which generally forms a major or essential part of an electric motor, a transformer and the like, and it also relates to a method of producing such an iron core assembly.
2. Description of the Related Art
For example, an iron core assembly of the type mentioned above has been used in a conventional electric motor, as disclosed in Japanese unexamined patent publication (laid-open) No. 9-191588. As shown in FIGS. 58 and 59, such a kind of conventional iron core assembly comprises a predetermined number of core members 1 stacked or laminated one over another, each core member 1 being formed of a plurality of core segments 1a which are connected together by way of a plurality of thin portions 1b. In order to improve winding property or efficiency, the stacked core members 1 in their states as shown in FIG. 59 are wound with wires 2 by means of a winding machine (not shown), and the respective thin portions 1b thereof are then bent properly to form an annular or ring-shaped core assembly as shown in FIG. 58.
Since a conventional iron core assembly is constructed in the above-described manner, when a ring-shaped iron core assembly is formed, every two adjacent core segments 1a facing each other through a thin portion 1b, and end faces of each edge portion of core segments 1a located on opposite ends of each core member 1, will undesirably produce some rough surface portions and some working size errors during a press punching process. As a result, every two adjacent core segments 1a will have to be brought together with an undesirable clearance of several micrometers (xcexcm) to ten-odd micrometers (xcexcm) formed therebetween. Due to the existence of such kind of clearances, a magnetic resistance will undesirably be increased, resulting in a problem that the magnetic performance of the iron core assembly is deteriorated.
Further, since. each of the core members 1 forming an iron core assembly is usually provided on the surface thereof with a skin layer. Such a kind of skin layer is useful in hampering the passing of an magnetic flux therethrough so as to inhibit a possible eddy current loss. For this reason, if there is no such kind of skin layer existing on the end faces of punched portions, an undesired eddy current will occur over the entire area of each end face of each core segment 1a in the laminating direction. Because of the occurrence of the eddy current, an undesired iron loss will happen, thus undesirably affecting a desired magnetic performance.
Moreover, on each of the above end faces, since a holding force intended to act against an external force in parallel with the end faces is relatively weak, the iron core assembly as a whole has only low rigidity. In particular, if an electric motor is a type in which a force caused by magnetism exerts on its iron core assembly, it will be difficult to ensure a required strength for the motor.
In addition, since each thin portion 1b is bent in a manner such that a circular configuration is formed as a whole, it is difficult to mechanically ensure high precision for an electric motor. Further, since bending treatment has to be performed for several times in order to form the desired circular configuration, some cracks will possibly occur in the thin portions 1b, resulting in some problems in which not only the mechanical strength is reduced, but also desired magnetic performance is deteriorated because the cracks will cause an increase in the magnetic resistance of a magnetic circuit.
In view of the above, the present invention is intended to obviate the above-discussed problems encountered with the conventional iron core assemblies, and has for its object to provide an improved iron core assembly of the character described and a method of manufacture thereof which are suitable for mass production and which are capable of inhibiting a possible increase in the magnetic resistance and a possible occurrence of an eddy current so as to obtain improved magnetic performance, thereby ensuring improved rigidity and increased mechanical precision for the iron core assembly.
Bearing in mind the above object, according to a first aspect of the present invention, a method for producing an iron core assembly comprises alternately laminating a plurality of first core members, each of the first core members is formed of a plurality of independent plate-shaped first core segments arranged in planar succession, to a plurality of second core members, each of the second core members is formed of a plurality of independent plate-shaped second core segments arranged in planar succession, one over another in such a manner that first inter-segment positions defined between adjacent first core segments of each first core member are offset from second inter-segment positions defined between adjacent second core segments of each second core member in a longitudinal direction of said first and second core members, with end portions of said first and second core segments which adjoin each other in a laminating direction in which said first and second core members are laminated being overlapped each other; wherein, as a result of the laminating, couplers, which comprise concave portions and convex portions formed at the end portions of adjacent core segments of said first and second core members, form rotatable shafts in the laminating direction thereby to couple adjacent end portions of the respective core segments to each other for rotation relative to each other.
With this arrangement, it is possible to provide an iron core assembly which is suitable for mas production and can be improved in its magnetic performance and mechanical strength.
In a preferred form of the first aspect of the invention, the coupling means couples together edge portions of those core segments which adjoin each other in the laminating direction of the first and second core members. Thus, it is possible to further improve the magnetic performance and mechanical strength of the iron core assembly.
According to a second aspect of the present invention, a method for producing an iron core assembly comprises alternately laminating a plurality of first core members, each of the first core members is formed of a plurality of first core segment blocks arranged in succession, each of the first core segment blocks comprises a plurality of laminated independent plate-shaped first core segments, to a plurality of second core members, each of the second core members is formed of a plurality of second core segment blocks arranged in succession, each of the second core segment blocks comprises a plurality of laminated independent plate-shaped second core segments, one over another in such a manner that first inter-segment positions defined between adjacent first core segment blocks of each first core member are offset from second inter-segment positions defined between adjacent second core segment blocks of each second core member in a longitudinal direction of said first and second core members, with end portions of said first and second core segment blocks which adjoin each other in a laminating direction in which said first and second core members are laminated being overlapped each other; wherein, as a result of the laminating, couplers, which comprise concave portions and convex portions formed at the end portions of adjacent core segments blocks of said first and second core members, to form rotatable shafts in the laminating direction thereby to couple adjacent end portions of the respective core segment blocks to each other for rotation relative to each other.
With this arrangement, the magnetic performance and mechanical strength of the iron core assembly can be improved, and the number of component parts of the core assembly can be reduced, thus enhancing productivity. Beside, when the core segment blocks are to be rotated tooth by tooth, such rotation becomes easy due to reduced friction.
The above and other objects, features and advantages of the present invention will more readily apparent from the following detailed description of preferred embodiments of the invention when taken in conjunction with the accompanying drawings.